In the triangle, we are given angles of 90 degrees, and one of 74 degrees. we also know that all angles in a triangle must sum up to 180 degrees, so we add both 74 and 90 degrees together and get 164 degrees. Then take 180 and take 164 away to solve for angle b. Angle B is then 16 degrees.
Finally, on a line, and in this case, a + b, must sum up to 180. So we just do 180 minus b, or 180 minus 16, and we get that angle a is 164.
